The mammary system is comprised of the mammary glands or breasts and is present in all mammals. Mammary glands are typically arranged in two parallel rows extending from the underside of the chest to the groin area, along the outside of the body wall. The mammary glands are joined together in a chain on each side. Dogs usually have five mammary glands whereas cats usually have four. In males, mammary glands exist in a rudimentary state. The chief function of the mammary glands is to provide milk and nourishment to the newborn. Common diseases of the mammary system in dogs and cats include: mastitis (inflammation/infection), galactostasis (abnormal accumulation of unexcreted milk), agalactia (failure to produce and excrete milk), galactorrhea (excessive or inappropriate production and release of milk), and mammary gland tumors. Mammary gland tumors are a cancer of the breast tissues. These tumors are similar to breast cancer in women, and can be lethal in dogs and cats.
Mammary gland tumors are the most common tumor developing in female dogs, particularly those not spayed. They are rare in males. Approximately 50 percent of these tumors are malignant (they can spread to the adjacent glands and lymph nodes) and 50 percent are benign (they do not spread elsewhere in the body). Mammary gland tumors occur in cats but are less common. They usually develop in older cats that have not been spayed and may also develop in cats prescribed progesterone medications. Siamese cats appear to have an increased risk for these tumors. Approximately 90 percent of these tumors are malignant.
The timing of an ovariohysterectomy, the removal of the ovaries and uterus, significantly impacts development of mammary gland tumors in dogs and cats. Dogs and cats spayed prior to their first estrus cycle (heat cycle) have less than a one percent risk, those spayed between the first and second estrus have an 8 percent risk, whereas those spayed after their second estrus cycle develop these tumors as commonly as dogs and cats that are not spayed. Spaying your dog and cat early in life can prevent these tumors.
If your pet develops a mammary tumor, it is best to do a full work-up or staging to thoroughly evaluate your pet’s health and determine if there are any underlying problems or evidence of metastasis. Treatment of mammary tumors can include:
- Mastectomy (surgical removal of the mass and associated mammary gland, and any involved lymph nodes),
- Ovariohysterectomy (if your pet is intact, spaying is recommended),
- Radiation therapy, and/or
- Anti-estrogen therapy (anti-hormone therapy).
- Approximately 50% of mammary tumors are malignant, and approximately 50% are benign. Any breed is susceptible, however there is an increased predisposition in Poodles, Cocker Spaniels, Dachshunds, Terriers, and German Shepherd dogs.
- The development of mammary tumors in the dog is clearly hormone dependent.
- The risk for malignant tumors in dogs spayed prior to the 1st estrus (before their 1st heat cycle) is 0.05%.
- The risk for malignant tumors in dogs spayed after the 1st estrus (between their 1st and 2nd heat cycles) is 8%.
- HOWEVER, the risk for malignant tumors in dogs spayed after the 2nd estrus (after their 2nd heat cycle) rises to 26%.
- Later spaying does NOT reduce the risk for malignant tumors, while the risk for benign tumors seems reduced by spaying even at a later age. Spaying your dog eliminates the risk of uterine and ovarian cancers, as well as eliminates the risk of pyometra (infection of the uterus).
- Approximately 90% of mammary tumors in cats are malignant. Any breed is susceptible, however there is an increased incidence in Siamese and domestic short-haired cats.
- Hormonal influences seem to be involved in the pathogenesis of mammary tumors in the cat.
- A study found that cats spayed at 6 months of age had approximately 7-fold REDUCED risk of mammary cancer compared to intact cats.
- More recent studies have also been able to show that spayed cats have a 40% to 60% lower risk of developing mammary cancer than intact cats.
We will be going PASSIONATELY PINK during the week of October 17th thru October 22nd in support of breast cancer awareness for 2011! We will be wearing PINK, and accepting any donations to contribute to the cause.
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Please call us at 706-546-7879 if you are interested in having your dog or cat spayed for these health benefits. Spaying your dog or cat eliminates the risk of uterine and ovarian cancers and infection (pyometra), and decreases the risk of mammary gland tumors as well.